1. Field of the Invention
The present invention relates to a liquid crystal display (LCD) and method for manufacturing the LCD. More specifically, the present invention relates to a liquid crystal display (LCD) and method for manufacturing the LCD, in which the opening efficiency of the LCD is increased.
2. Description of the Related Art
Generally, a thin film transistor liquid crystal display (TFT-LCD) comprises a lower substrate, an upper substrate, a liquid crystal, and a polarized light plate. The lower substrate includes a thin film transistor and a pixel electrode, and the upper substrate includes a color filter and a common electrode. The liquid crystal is placed between the upper and lower substrates, while the polarized light plate, which polarizes natural light, is attached to an exterior surface of the two substrates.
To block unwanted light, the upper substrate includes a conventional black matrix. Specifically, the black matrix passes only that light which is passed by the pixel electrode and the color filter. When the black matrix is formed on the upper substrate, however, an adhesion margin of approximately 6-10 μm is employed to account for any misalignment between the upper and lower substrates. The adhesion margin cause the black matrix to overlap the pixel electrode, which, in turn, significantly decreases the opening efficiency of the LCD.
To overcome this problem, the it has been proposed to form the black matrix on the lower substrate. This reduces the adhesion margin and increases the opening efficiency. FIG. 1 is a plan view of an LCD in which the black matrix is formed on the lower substrate.
Referring to FIG. 1, the LCD comprises a scan line 11L, a signal line 13L, a plurality of pixel electrodes 17, a black matrix 19, and a thin film transistor 20. Thin film transistor 20 is located at a region where signal line 13L crosses scan line 11L, and further includes, a gate electrode 11G, a gate insulating film 12 (see FIG. 2), a source electrode 13S, a drain electrode 13D and an active layer 15. Gate electrode 11G connects to scan line 11L and source electrode 13S connects to signal line 13L. Drain electrode 13D is formed on the opposite side of gate electrode 11G where source electrode 13S is formed. Drain electrode 13D connects to a corresponding pixel electrode 17.
The hatched area of FIG. 1 represents black matrix 19, which completely covers a metal pattern of the LCD. Specifically, black matrix 19 covers signal line 13L and scan line 11L, but does not cover a part of drain electrode 13D. Black matrix 19 also covers part of pixel electrode 17 to prevent light from entering between the metal pattern and pixel electrode 17.
FIGS. 2A to 2C are sectional views taken along lines A-A′, B-B′, and C-C′, respectively, of FIG. 1. Referring to these figures, black matrix 19 is formed on an interlayer insulating film 14. Interlayer insulating film 14 covers scan line 11L, signal line 13L, and thin film transistor 20. Black matrix 19 covers insulating film 14 at the area between pixel electrodes 17. As a result, black matrix 19 prevents light from passing between pixel electrode 17 and each of scan line 11L, signal line 13L, and thin film transistor 20.
In the LCD shown in FIGS. 1 and 2A and 2B, black matrix 19 is formed on the lower substrate, thus reducing the required adhesion margin. Furthermore, forming black matrix 19 on the lower substrate also increases the opening efficiency by reducing the amount black matrix 19 overlaps pixel electrode 17. However, an adhesion margin of about 2-3 μm must still be used to account for any misalignment between the upper and lower substrates. Moreover, an adhesion margin of about 2-3 μm substantially reduces the opening efficiency of the LCD. An additional problem with the above LCD is that an additional mask pattern is required to form black matrix 19, thus reducing the production yield.